Field of the Invention
This application relates generally to electronic protection circuitry. More, specifically, the application relates to a remote activated fuse and circuit for using the remote activated fuse.
Introduction to the Invention
Protection circuits are utilized in electronic circuits to isolate failed circuits from other circuits. For example, a protection circuit may be utilized to prevent a cascade failure of circuit modules in an electronic automotive engine controller. Protection circuits may also be utilized to guard against more serious problems, such as a fire caused by a power supply circuit failure.
One type of protection circuit is an ordinary glass fuse. The glass fuse includes a conductor that behaves like a short circuit during normal operation. When the current through the conductor exceeds a threshold, the conductor opens and current flow stops.
Another protection circuit is a thermal fuse that transitions between short circuit and open circuit modes of operation when the temperature of the thermal fuse exceeds a specified temperature. To facilitate these modes, thermal fuses include a conduction element, such as a fusible wire, a set of metal contacts, or a set of soldered metal contacts, that can switch from a conductive to a non-conductive state. A sensing element may also be incorporated. The physical state of the sensing element changes with respect to the temperature of the sensing element. For example, the sensing element may correspond to a low melting metal alloy or a discrete melting organic compound that melts at an activation temperature. When the sensing element changes state, the conduction element switches from the conductive to the non-conductive state by physically interrupting an electrical conduction path.
One disadvantage with existing fuses is they are only configured to activate (i.e., open) during a single fault condition, such as either when the current exceeds a threshold or when a temperature exceeds a threshold.